I agree, nothing wrong with what you did. WYNN is a nice momentum stock even when it's already made a very large run as you can see from the opening hour's action (more than a 2 pt range down and up).
Trading AAPL, AMZN and POT, I found that the opening 90 mins provided the best moves and I started using a 1-min chart to catch an early entry, hoping to possibly catch a good trend or at least one of the stronger moves of the day. I generally avoid the first 5 mins' noise (unless a signal is simply too good to pass up).
So if I were looking for an early entry with WYNN Friday, I study multiple time frames first. I see on the daily chart that it tends to have a very strong up day, then pull back for 1-3 days. The pullback is never a full retracement of the up move, in fact lately it's been less than 50% retracement. I also note that short interest is high, and it just closed at a 52-week high on a very strong up day. None of the investors are in any pain at all, and have no reason to sell. Short term traders may be looking to take at least partial profits if price breaks down Thursday's close (86.23).
So my trading plan for early entry would be to short any selling pressure off the open, meaning if price didn't go up right away, I'd be short immediately.
My trading plan for conservative entry would be to short a tick or two below 86.23.
My initial profit target would be at a price greater than 50% retracement of the last move up and my stop no greater than Thursday's high (86.91). If you go with a 40% retracement (approx 2.50) your target off Thursday's high will be 84.41. Once price moves 40-50 ticks in your favor, move the stop to break even. You're counter-trend trading so give the play no mercy stop-wise.
Price opens gapped up slightly, but falls right away and the short entry is triggered. Looking at the chart, I can tell you right now that I personally would have covered when price found support near the round number 85.00. Even if I gave the trade more time, I would've ended up covering around the same price, when price left a long hammer behind on the 9:51am bar (3-min chart, which I use for stock trading).
That hammer was a decent enough long signal, but knowing me I'd still have too much short bias to go long. That's still a big defect of mine, forming opinions instead of responding automatically to the price action signals.